Q and Pentax K adapter

Started Sep 21, 2012 | Discussions thread
snostorm Senior Member • Posts: 2,044
Re: Q and Pentax K adapter

Chris Dennehy wrote:


I have been getting quite interested in the Q especially since the arrival of the Q10.

I have a Pentax DSLR and quite a number of manual lenses, has anybody used the K mount adapter and with what sort of results.

I am primarily thinking of my M series lenses which are small and light enough and would give some added impetus to the zoom end of things, if my calculations are correct the 100mm should get me somewhere in the region of 550mm.

As the years roll on the DSLR is getting too heavy for me.

Hi Chris,

First of all, I bought the Q primarily for use with adapted tele and macro lenses and find it more useful to think in terms of "crop" factor compared to APS-C (3.67x) since I've been shooting Pentax DSLRs for over 6 years, and APS-C is my dominant reference on FL (FOV). I think of a 100mm f2.8 lens on my Q as giving me equivalent "reach" and lens speed to a 370mm f2.8 lens on my K-5 (if there was such a creature).

A significant factor that also needs to be considered is the max aperture. This is a very real advantage, since a fast 100mm (say f2.8) is neither physically large nor expensive compared to it's 300+mm DSLR counterpart. My D FA 100 f2.8 Macro takes 49mm filters and weighs just over 12 oz compared to my FA* 300 f2.8 which takes 112mm filters and weighs 6 lbs, 10 oz. This isn't really a fair comparison though, since the FA*300 on APS-C doesn't have as much "reach".

Don't be confused by those who will say that a 100mm f2.8 will actually be "equivalent" to a 370mm f8 on an APS-C camera -- or some such -- they are talking about DOF equivalence, not exposure. An f2.8 lens will still expose at f2.8, so will be appropriate to give 2 stop faster shutter speeds for a given light level than the

typical XX-300mm f4-5.6 DSLR zoom. It will have deeper DOF, but that is actually usually an advantage for ultra tele shooting which suffers from too shallow DOF in many applications.

The small, extremely well built M series lenses are very appropriate for adaptation to the Q. Their smooth focus ring feel also should help considerably.

There are some issues. The Q is a mirrorless design, so any problems with MF using the LCD as a viewfinder will be present in the Q. I have found that using an LCD loupe like the Hoodman HoodLoupe helps considerably since it eliminates the washed out LCD in sunlight and allows me to stabilize the camera against my face as opposed to holding the camera at arms' length. Also the 4x magnified focus assist helps considerably with critical focus.

Also, at this time, SR is not available for use with adapted lenses. Pentax has assured us that a firmware update is going to allow manual input of FL and make SR available with adapted lenses, but are a bit unclear how exactly this will be implemented. This should make SR available for both the Q and Q10 but we'll have to wait and see. . .

All that being said, IMO, the Q works well as a digital TC, offering previously unprecedented potential super tele lens speed and "reach" as well as very high macro magnifications with SLR lenses at affordable prices and easy to handle size and weight.

Here are a few shots with the Q + adapted D FA 100 f2.8 Macro. Please excuse the underexposure. These were all handheld, PP'd to taste and downsized for posting.

This is an example of the macro magnification on the Q. This is the full frame of a shot of a US Quarter with the Q. Since a Quarter is 24.26mm in diameter, it's a bit wider than the width of the frame for a Pentax DSLR (23.77mm) at 1:1


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